1. Field of the Invention
The invention relates to a battery operated device having an electrically operated functional unit and an electrochemical voltage source, which are housed together in an essentially gas-tight device housing, in particular an implantable medical-electronic device having such a basic construction.
2. Description of the Related Art
Devices of this type, especially also implantable medical-electronic devices, such as cardiac pacemakers, implantable defibrillators, neurostimulators, or implantable insulin or medication pumps, etc., are known in a great manifold of designs. They currently usually contain a lithium ion secondary element (also referred to in short as a “lithium battery” hereafter) as the power source, which has a gas-tight welded metal housing, normally made of stainless steel or titanium.
For such batteries, this complex housing is a significant cost factor, because of which a simpler solution has been sought for some time for reasons of cost. Plastic housings are fundamentally to be taken into consideration for this purpose, because of the easy producibility and extraordinarily low costs.
The use of batteries—especially lithium batteries—having housings made of plastic has not been possible until now for medical implants, because typically liquid or gel electrolytes based on organic solvents or solvent mixtures are used in lithium batteries. Organic carbonates, ethers, or esters are preferably used. Organic polymers are permeable to vapors of the solvents—above all at elevated temperatures—so that if a plastic housing is used in a gas-tight sealed implant, solvent may reach the inner chamber of the implant. This solvent may react with other components of the implant, such as electronic components or insulation, and trigger malfunctions or defects.